Waste disposer units, such as are typically used in the kitchen, in commercial establishments or on marine vessels, are usually driven by an electric motor, which rotates one- or two-stage cutters at high speed, often with considerable noise. In addition to requiring electrical wiring, there is a potential hazard of having electrical connections and water in the same structure, requiring very positive means to maintain absolute separation between the water and the electricity. Further, if the cutters are jammed by an obstruction, such as a bone, a piece of flatware or other hard object, the motor normally stalls and may become damaged. If an overload switch is installed it must be reset, and it is often in an inaccessible location. With the type of cutters normally used for electrical waste disposers, it is possible for fairly large particles to pass through the disposer and accummulate in a waste pipe bend, possibly causing ultimate blockage of the drain, particularly if insufficient flush water is used.
Water driven units have been developed. A typical early example is disclosed in U.S. Pat. No. 3,700,178, which has a reversing valve actuated by a drive piston at each end of its stroke. This particular structure could result in a jammed condition when a hard object entered the disposer in a partial stroke position. A substantially improved version is shown in U.S. Pat. No. 4,082,229, which discloses a practical water powered waste disposer capable of efficient operation at normal dynamic water pressure of approximately 30 pounds. However, in locations where the water pressue is below 30 pounds, the waste disposer shown in that patent tends to operate with less efficiency for its intended purpose. Certain built-in leakage of water within the unit is not only permissible, but is necessary for the unit to operate properly. However, this leakage resulted in requiring a certain minimum (30 pounds) water pressure which may not be available in some locations.